Reduction jack for spinal rod placement and method of use

ABSTRACT

A reduction jack for placing a spinal rod within a rod channel of a bone fixation screw includes a mounting stem having a tubular body, a plurality of teeth disposed on the body, a pair of legs projecting from the body, and catches disposed on the legs for engaging the bone fixation screw. A reduction sleeve at least partially encircles the mounting stem. A gear assembly is mounted on the reduction sleeve and engages the teeth on the body such that manipulation of the gear assembly facilitates movement of the reduction sleeve along the mounting stem. A first pawl is pivotably mounted to the reduction sleeve and resiliently biased against the teeth on the body, the first pawl being pivotable between a first position where the first pawl engages the teeth on the body and a second position wherein the first pawl does not engage the teeth on the body.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to reduction jacks used for reducingspinal rods into rod channels of bone fixation screw.

2. The Relevant Technology

There are a number of surgical procedures and treatments that requirethe immobilization of a portion of the spine. For example, vertebralfusion is a medical procedure where adjacent vertebrae of the spine arefused together. As part of this procedure, a mechanical stabilizingsystem is implanted in the patient which immobilizes the adjacentvertebrae. Such stabilizing systems can also be used in the treatment ofspinal trauma and spinal curvature such as scoliosis.

A typical spinal stabilizing system includes, in part, a plurality ofbone fixation screws that are mounted on each side of each consecutivevertebra that is being fused together. Each bone fixation screw has acollar with a U-shaped rod channel formed thereon. An elongated, metal,spinal rod is received within the rod channels of the aligned bonefixation screws on each side of the spine. Once the spinal rods arepositioned, fasteners are threaded onto the collars so as to rigidlylock the spinal rods to the bone fixation screws, thereby securing eachvertebra in a fixed relative location.

Because the vertebrae are often out of alignment at the start of theprocedure, the spinal rods may freely be received within some of the rodchannels of the bone fixation screws but may be misaligned with others.To that end, reduction jacks are used to reduce or move the spinal rodsinto the rod channels from which the spinal rods are misaligned.

A reduction jack typically includes a base that removably mounts to thebone fixation screw and captures the spinal rod, a reducer that engagesthe base, and a mechanical drive assembly. The drive assembly ismanually operated and is used to move the reducer relative to the baseso that the reducer pushes against the spinal rod and forces the spinalrod into the rod channel of the bone fixation screw. Moving the spinalrod into the rod channel can occur as a result of moving the spinal rodand/or the corresponding vertebrae.

Although reduction jacks are useful for their intended purpose, theytypically have a number of shortcomings. For example, the drive assemblytypically moves the reducer at a very slow rate. As such, it can take anextended period of time to even move the reducer to the point where itinitially engages the spinal rod. It can also take an extended timeperiod to move the reducer back to its original position so that thereduction jack can be removed from the bone fixation screw. In additionto being time consuming to use, conventional reduction jacks can bedifficult to attach to the bone fixation screws. Likewise, inconventional reduction jacks it can often be difficult to access and/ormanipulate the drive assembly that moves the reducer relative to thebase. Furthermore, some conventional reduction jacks can obstruct thebone fixation screw making it difficult to align and attach the fastenerto the bone fixation screw.

Finally, the reduction jacks can also be used as a lever, when attachedto a bone fixation screw, to move the vertebrae to a desired position ororientation. Conventional reduction jacks can often be too long or tooshort for their desired placement and use.

Accordingly, what is needed in the art are reduction jacks that overcomeone or more of the above shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. In the drawings,like numerals designate like elements. Furthermore, multiple instancesof an element may each include separate letters appended to the elementnumber. For example two instances of a particular element “20” may belabeled as “20 a” and “20 b”. In that case, the element label may beused without an appended letter (e.g., “20”) to generally refer to everyinstance of the element; while the element label will include anappended letter (e.g., “20 a”) to refer to a specific instance of theelement.

FIG. 1 is a perspective view of a pair of reduction jacks reducingspinal rods into rod channels of bone fixations screws attached to aspine;

FIG. 2 is a perspective view of the bone fixation screw and spinal rodof FIG. 1;

FIG. 3 is a perspective view of the reduction jacks and bone fixationscrews of FIG. 1 outside of the spine;

FIG. 4 is a partially exploded view of one of the reduction jacks shownin FIG. 1;

FIG. 5 is an enlarged perspective view of the mounting stem of thereduction jack shown in FIG. 4;

FIG. 6 is a perspective view of the proximal end of the mounting stemshown in FIG. 5;

FIG. 7 is a perspective view of the distal end of the mounting stemshown in FIG. 5;

FIG. 8 is a perspective view of the side of the reduction sleeve of thereduction jack shown in FIG. 4;

FIG. 9 is a perspective view of the distal end of the reduction sleeveshown in FIG. 8;

FIG. 10 is a perspective view of the front of the reduction sleeve shownin FIG. 8;

FIG. 11 is a partially exploded perspective view of the reduction jackshowing the gear assembly attached to the reduction sleeve;

FIG. 12 is a perspective view showing how the gear assembly and pawls ofFIG. 11 engage the teeth on the mounting stem;

FIG. 13 is a cross sectional side view of the assembled reduction jackshown in FIG. 11;

FIG. 14 is a partially exploded view of the extension of the reductionjack shown in FIG. 1; and

FIG. 15 is an exploded view of the bridge of the reduction jack shown inFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The embodiments described in the detaileddescription, drawings, and claims are not meant to be limiting. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presentedherein. It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in theFigures, can be arranged, substituted, combined, separated, and designedin a wide variety of different configurations, all of which areexplicitly contemplated herein. It will also be understood that anyreference to a first, second, etc. element in the claims or in thedetailed description is not meant to imply numerical sequence, but ismeant to distinguish one element from another unless explicitly notedotherwise.

In addition, as used in the specification and appended claims,directional terms, such as “top,” “bottom,” “up,” “down,” “upper,”“lower,” “proximal,” “distal,” “horizontal,” “vertical,” and the likeare used herein solely to indicate relative directions and are nototherwise intended to limit the scope of the invention or claims.

Depicted in FIG. 1 is a pair of reduction jacks 10A and 10B coupledtogether by a bridge 12 and incorporating features of the presentinvention. Reduction jacks 10 are used in association with bone fixationscrews 14 and spinal rods 40. Bone fixation screws 14 are mounted onopposing sides of adjacent vertebrae 15 while spinal rods 40 are securedto and longitudinally extend between aligned bone fixation screws 14.Bone fixation screws 14 and spinal rods 40 are commonly used inprocedures for fusing together adjacent vertebrae 15 but can also beused in other spinal applications. In general, reduction jacks 10 areused for reducing spinal rods 40 into rod channels on bone fixationscrew 14 and derotating select vertebrae 15 that may be out ofalignment.

More specifically, as depicted in FIG. 2, each bone fixation screw 14comprises a threaded shaft 16 having a tip end 18 configured forthreading into a vertebra and an opposing fixation end 20. Disposed onfixation end 20 is a collar 22. Collar 22 can be either pivotallymounted on fixation end 20, as depicted, so as to form a polyaxial screwor can be rigidly fixed on fixation end 20. Collar 22 has an interiorsurface 24, an exterior surface 26, and a U-shaped rod channel 28 thatlaterally passes through collar 22. Collar 22 terminates at an end face27 having an opening 29 formed thereat that communicates with rodchannel 28. Recessed on exterior surface 26 on opposing sides of rodchannel 28 is a pair of retention notches 30A and 30B. Formed oninterior surface 24 on opposing sides of rod channel 28 are threads 32.

Elongated spinal rod 40 typically has a cylindrical configuration and issized so that it can be received within rod channel 28. A fastener 42has a top surface with a driver socket 44 formed thereon and a threadedside surface 46 extending along the length thereof. Fastener 42 isconfigured to be received within opening 29 of collar 22 so that it canbe screwed into rod channel 28 by engaging threaded side surface 46 withthreads 32. When spinal rod 40 is received within rod channel 28, theengagement of fastener 42 with collar 22 secures spinal rod 40 withinrod channel 28. Furthermore, fastener 42 can be further threaded intorod channel 28 until spinal rod 40 is compressed between fastener 42 andeither collar 22 or fixation end 20 of shaft 16, thereby fixing spinalrod 40 relative to collar 22. By securing spinal rod 40 to each bonefixation screw 14 located on consecutive vertebrae 15 (FIG. 1), spinalrod 40 fixes the corresponding vertebrae relative to each other. Thelength of spinal rod 40 can vary depending upon the number ofconsecutive vertebrae spinal rod 40 is used for securing together.Again, separate spinal rods 40 and corresponding bone fixation screws 12are used on opposing sides of vertebrae 15.

It is appreciated that bone fixation screws 14 can come in a variety ofdifferent designs, configurations, and sizes that can be used with avariety of different types of fasteners. In general, however, all bonefixation screws include a rod channel configured to receive a spinal rodand a fastener that can attach to the bone fixation screw for securingthe spinal rod within the rod channel.

As depicted in FIGS. 3 and 4, reduction jacks 10A and 10B are, in part,used for reducing or moving spinal rod 40 into rod channel 28 of acorresponding bone fixation screw 14. Each reduction jack 10 comprises,in part, an elongated tubular mounting stem 50 that couples with bonefixation screw 14, a reduction sleeve 52 that at least partiallyencircles and moves along the length of mounting stem 50, and anextension 54 that removably couples with an end of mounting stem 50. Asdepicted in FIG. 5, mounting stem 50 comprises an elongated tubular body60 having an interior surface 62 and an exterior surface 64 thatlongitudinally extend between a proximal end 66 and an opposing distalend 68. Proximal end 66 terminates at a proximal end face 69. Interiorsurface 62 bounds a passageway 70 longitudinally extending therethrough.Exterior surface 64 includes a front face 72, an opposing back face 74and side faces 76 and 78 extending therebetween. In one embodiment, eachface 72, 74, 76, and 78 is substantially planer so that exterior surface64 has a substantially square or rectangular transverse cross sectionwith the intersecting corners being rounded or chamfered. Formed alongfront face 72 are a plurality of teeth 80 that are orientated so as tolongitudinally extend between side faces 76 and 78. Teeth 80 combine toform a rack 81 that typically extends over a majority of the length offront face 72 and typically extends at least 50% of the length or morecommonly at least 70% or 80% of the length.

As depicted in FIG. 6, a pair of locking channels 82A and 82Blongitudinally extend along a length of side faces 76 and 78 at proximalend 66, respectively, and intersect with proximal end face 69. A pocket84 (FIG. 5) is further recessed at the distal end of each alignmentchannel 82. Guide post 86A and 86B outwardly project from side faces 76and 78, respectively, at or towards distal end 68. Each guide post 86projects from a partially cut out section 88 (FIG. 5) of body 60.Section 88 flexes relative to the remainder of body 60 so that guidepost 86 are resiliently flexible relative to side faces 76 and 78. Thatis, guide post 86 can be pressed into side faces 76 and 78 and will thenresiliently rebound to project out from side faces 76 and 78.

Returning to FIG. 5, projecting from distal end 68 of body 60 are a pairof legs 90A and 90B. Each leg has a proximal end 92 and an opposingdistal end 94. Proximal end 92 of leg 90A is rigidly fixed to distal end68 of body 60. For example, in one embodiment leg 90A is integrallyformed as a signal unitary member with body 60. In contrast, proximalend 92 of leg 90B is hingedly coupled to distal end 68 of body 60 so asto have a pivot axis 103. As such, distal end 94 of leg 90B can pivotoutward and away from leg 90A by pivoting about axis 103. Legs 90A and90B both have an interior surface 96 and an opposing exterior surface 98extending between opposing ends 92 and 94. Interior surface 96 of legs90A and 90B bound a passageway 100 therebetween that extends along thelength of legs 90. Passageways 70 and 100 are longitudinally aligned andare in communication with each other so that they jointly form apassageway 102 that extends the full length of mounting stem 50 fromproximal end 66 to distal end 94. As depicted in FIG. 7, radiallyinwardly projecting from interior surface 96 of each leg 90A and 90B atdistal end 94 is a catch 104A and 104B, respectively. As will bediscussed below in greater detail, catches 104 are configured to bereceived within retention notches 30 (FIG. 2) on bone fixation screws 14to enable legs 90 to firmly engage bone fixation screws 14. In oneembodiment of the present invention, means are disposed on legs 90 forengaging bone fixation screws 14. One example of such means is catches104. In alternative embodiments, however, catches 104 can come in avariety of different configurations and can be placed in a variety ofdifferent orientations and positions on legs 90 depending on theconfiguration, position, and orientations of retention notches 30located on bone fixation screws 14.

U-shaped slots 106A and 106B are formed between the two pairs ofadjacent side edges of legs 90A and 90B. Slots 106A and B and passageway100 combine to form a rod channel 108 that transversely extends betweenlegs 90A and 90B and which is configured to receive spinal rod 40.

In one embodiment of the present invention, means are provided forapplying a force that resiliently urges distal ends 94 of legs 90A and90B away from each other. By way of example and not by limitation, aspring 105 is provided having a first end 107 and an opposing second end109. Spring 105 is in the form of an elongated rod comprised of aresiliently flexible material, such as a metal, which is curved or bentin its relaxed state. First end 107 of spring 105 is secured to body 60at distal end 68 of front face 72. First end 107 can be secured such asby being welded or press-fit on body 60. First end 107 can also bereceived within an opening on body 60 or otherwise secured thereto. Anotch 111 is recessed at proximal end 92 of leg 90 and second end 109 ofspring 105 is received within an opening 110 formed on an inside face ofnotch 111.

When legs 90A and 90B are received within reduction sleeve 52, as shownin FIG. 1, legs 90A and 90B are moved into parallel alignment as shownin FIG. 5. In this parallel alignment, spring 105, which naturally has acurve or bend, is moved to a more linear configuration so that spring105 applies a force to leg 90B that wants to resiliently urge distalends 94 of legs 90A and 90B away from each other. Specifically, theforce urges leg 90B to pivot about axis 103 away from leg 90A.Accordingly, when reduction sleeve 52 is removed from off of legs 90, asdiscussed below, legs 90 resiliently separate. This enables collar 22 ofbone fixation screw 14 (FIG. 2) to be easily placed between legs 90 forengaging therewith. It is appreciated that a variety of different springconfiguration can be used to urge separation of legs 90. For example acoil spring could extend between body 60 and leg 90B which stretches aslegs 90 are moved into parallel alignment. Other spring configurationscan also be used.

In an alternative embodiment, it is appreciated that leg 90A can also behingedly mounted to body 60. Likewise, a separate spring 105 can becoupled with leg 90A to apply a force the urges leg 90A to pivot awayfrom leg 90B. In another alternative embodiment, it is appreciated thatspring 105 need not be coupled with leg 90B. In this embodiment, leg 90Bcan be manually pivoted during attachment to bone fixation screw 14.

Turning to FIG. 8, reduction sleeve 52 comprises a tubular member 114having an interior surface 116 and an exterior surface 118 thatlongitudinally extend between a proximal end 120 and an opposing distalend 122. Interior surface 116 bounds a passage 124 that is configured toreceive mounting stem 50 as depicted in FIG. 4. Continuing with FIG. 8,elongated guide slots 128A and 128B (FIG. 9) are longitudinally alignedon opposing sides of tubular member 114 so as to communicate withpassage 124. Guide slots 128 are configured to receive guide post 86(FIG. 5) of mounting stem 50.

Specifically, as depicted in FIG. 4, when mounting stem 50 is receivedwithin passage 124 of reduction sleeve 52, guide post 86A and B arereceived within locking slots 128A and B, respectively. Reduction sleeve52 can then move linearly along mounting stem 50 between a first orraised position as shown in FIG. 4 where guide posts 86 are located atthe distal end of guide slots 128 and a second or lowered position asshown in FIG. 1 where guide posts 86 are located at the proximal end ofguide slots 128. Guide posts 86 and guide slots 128 thus both limit thelongitudinal movement of reduction sleeve 52 along mounting stem 50 sothat reduction sleeve 52 does not unintentionally become disengaged frommounting stem 50 and keep reduction sleeve 52 properly oriented onmounting stem 50. That is, posts 86 prevent reduction sleeve 52 fromrotating about mounting stem 50. Although reduction sleeve 52 is shownas being circular so that it complete encircles mounting stem 50, in analternative embodiment reduction sleeve 52 can have a C-shapedtransverse cross section.

Also formed on tubular member 114 are viewing slots 130A and B that areformed distal of guide slots 128. Viewing slots 130 are in longitudinalalignment with guide slots 128 and extend through tubular member 114 soas to communicate with passage 124.

As depicted in FIG. 9, distal end 122 of tubular member 114 terminatesat a distal end face 132 that has a pair of arched engagement grooves134A and B formed thereon. Engagement grooves 134 are used to receivespinal rod 40 in positive engagement so that reducing sleeve 52 can moreefficiently be used in reducing spinal rod 40 into rod channel 28 (FIG.2) of bone fixation screw 14.

Turning to FIG. 10, mounted on proximal end 120 of tubular member 114 isa housing 140. In general, housing 140 includes a first arm 142 and asecond arm 144 that longitudinally extend along tubular member 114.Mounted between arms 142 and 144 is a compartment 146 that extendsthrough tubular member 114 so as to communicate with passage 124. Firstarm 142 terminates at a proximal end face 148 and bounds a pocket 150.Pocket 150 extends longitudinally down first arm 142 and laterallycommunicates with compartment 146 through a side opening 143.

Turning to FIGS. 11 and 12, mounted on housing 140 is a gear assembly154. Gear assembly 154 comprises a first drive section 156 comprising abase 158 having a top surface with a drive socket 160 formed thereon.Drive socket 160 has a non-circular transverse cross section so that adriver can be received within drive socket 160 to facilitate rotationthereof. Base 158 has a bottom surface with a first bevel gear 162formed thereon. Drive socket 160 and first bevel gear 162 have a commoncentral axis 164 about which they rotate. Although not required, in thisembodiment axis 164 is disposed parallel to a central longitudinal axis165 extending through passageway 102 of mounting stem 50. Drive section156 is rotatably received within pocket 150 of housing 140 so that firstbevel gear 162 projects in compartment 146 through side opening 143. AC-shaped retention clip 166 retains drive section 156 within pocket 150by being snapped fit within an annular recess formed on interior surfaceof pocket 150.

Gear assembly 154 further comprises a second drive section 168 that isdisposed within compartment 146 of housing 140 and is rotatably mountedon an axle 170 that spans between arms 142 and 144. Second drive section160 includes a second bevel gear 172 that is disposed orthogonal tofirst bevel gear 162 and which meshes with first bevel gear 162 so thatrotation of first drive section 156 about axis 164 facilitates rotationof second drive section 168 about axis 171. Coupled with second bevelgear 172 is a pinion gear 174. Pinion gear 174 meshes with teeth 80 ofrack 81 so as to form a rack and pinion gear system. That is, rotationof first drive second 162 causes concurrent rotation of second drivesection 168 which, in turn, as a result of the engagement between piniongear 174 and rack 81 causes reduction sleeve 52 to selectively travel ineither direction along the length of mounting sleeve 50 depending on thedirection of the rotation of first drive section 156. In one embodiment,the diameter of bevel gears 162 and 172 can be smaller than the diameterof pinion gear 174 resulting in a mechanical advantage in the rotationof pinion gear 174 and thus in the movement of reduction sleeve 52.

It is appreciated that a variety of alternative gear assemblies can beused for selectively moving reduction sleeve 52 along the length ofmounting stem 50. The disclosed system, however, has the advantage thatdrive socket 160 is easy to access while passageway 102 remainsunobstructed. Furthermore, the system permits a mechanical advantagethrough gear ratios as desired.

Partially disposed within compartment 146 of housing 140 is a first pawl180A and a second pawl 180B. As depicted in FIG. 13, pawl 180A comprisesan elongated body 182 having an inside face 184 that extends between afirst end 186 and an opposing second end 188. Pawl 180A pivots about anaxle 190 that extends between and is secured to arms 142 and 144 ofhousing 140 (FIG. 11). Axle 190 has a central longitudinal axis 192(FIG. 12) that is disposed parallel to axis 171 and perpendicular toaxis 164. A pocket 194 is recessed on inside face 184 at second end 188.A spring 196 is received within pocket 194 and rests against a platform198 (FIG. 11) of housing 140. Spring 196 applies a resilient force topawl 180A that pushes pawl 180A into a forward rocked position.

Pawl 180A engages teeth 80 of rack 81 so as to form a ratchet.Specifically, forwardly projecting from inside face 184 at first end 186is a tapered catch lip 200. Pawl 180A is configured so that when gearassembly 154 is rotated so as to move reduction sleeve 52 toward distalend 94 of mounting stem 50 (FIG. 4), catch lip 200 automatically ridesover teeth 80 by pawl 180A moving from a forward rocked position to arearward rocked position wherein spring 196 is compressed. As catch lip200 passes over a tooth 80, pawl 180A resiliently moves back to theforward rocked position so that catch lip 200 is pressed back into thetrough between the next pair of teeth 80. However, unless pawl 180A ismanually moved to the rearward rocked position, catch lip 200 engageswith teeth 80 to preclude reduction sleeve 52 from freely slidingtowards proximal end 66 of mounting stem 50 (FIG. 4) even when gearassembly 154 is torqued for rotation in the opposite direction. Thus,pawl 180A permits reduction sleeve 152 to incrementally slide distallyon mounting stem 50 through the manipulation of gear assembly 154 butrestricts the movement of reduction stem 52 back towards the proximalend 66 of mounting stem 50.

As shown in FIG. 12, pawl 180B has substantially the same configurationas pawl 180A and is likewise biased toward the forward rocked positionby a corresponding spring 196. Like elements between pawl 180A and 180Bare identified by like reference characters. The only difference betweenpawl 180A and 180B is that the catch lips 200 of the two pawls 180 areoffset so that they engage teeth 80 at different locations.Specifically, for example, when catch lip 200 of pawl 180A is disposedat the bottom of a trough between teeth 80, catch lip 200 of pawl 180Bis disposed that the top of a tooth 80. This could be the same tooth, anadjacent tooth, or any other tooth. By using two pawls 180A and B inthis configuration, reduction sleeve 52 can be advanced and held alongmounting stem 50 at shorter intervals for more precise placement. Thatis, with only one pawl 180, reduction sleeve 52 can only be advanced andheld at intervals of the width of one tooth 80. In contrast, by usingtwo pawls 180A and B, reduction sleeve 52 can be advanced and held atintervals of one-half of the width of a tooth 80. It is appreciated thatpawls 180 and teeth 80 can come in a variety of different configurationsto produce the desired ratchet configuration.

As depicted in FIG. 4, a lever 210 is hingedly mounted to housing 140 ofreduction sleeve 52 and extends over gear assembly 154 and pawls 180. Asdepicted in FIG. 13, lever 210 has a proximal end 212 and an opposingdistal end 214 with an interior surface 216 extending therebetween.Proximal end 212 is hingedly coupled to a proximal end of housing 140 byan axle 218 extending between legs 142 and 144. A spring 220 (FIG. 11)is secured within a recess 222 formed on first leg 142 and biasesagainst interior surface 216 of lever 210 to resiliently hold lever 210in an extended position as shown in FIG. 13. When desired, distal end214 of lever 210 can be radially inwardly pressed into a depressedposition. In the depressed position, spring 220 is resilientlycompressed and distal ends 188 of both pawls 180A and B are inwardlypushed by interior surface 216 of lever 210. Pawls 180A and B are thusmoved into the rearward rocked position so that catch lips 200 aredisengaged from teeth 80. As a result, with lever 210 manuallydepressed, pawls 180A and B are disengaged from teeth 80 permittingreduction sleeve 52 to freely slide either proximally or distally alongmounting stem 50. Although pinion gear 174 remains engaged with teeth 80while reduction sleeve 52 slides along mounting stem 50, pinion gear 174freely rotates without hampering the movement of reduction sleeve. Oncereduction sleeve 52 is in a desired position, lever 210 can be releasedwhich then resiliently moves back to the extended position, therebycausing pawls 180 to resiliently move back to the forward rockedposition so as to engage teeth 80.

The method of using the assembled reduction jacks 10 will now bediscussed in greater detail. Initially, as depicted in FIG. 1, bonefixation screws 14 are secured on opposing sides of adjacent vertebrae15 which are desired to be fused together or otherwise stabilized ormanipulated. Bone fixation screws 14 are typically threaded into thepedicles of each vertebra 15. Bone fixation screws 14 are typicallyattached with fastener 42 removed so that rod channels 28 are openlyexposed. Next, spinal rod 40 having a desired contour for thepositioning of vertebrae 15 is received within or is aligned with thecorresponding rod channels 28 (FIG. 2) of the aligned bone fixationscrews 14. Because spine rod 40 is rigid and some of the vertebrae arenot in the desired orientation, spinal rod 40 will typically not nestwithin each of the rod channels 28. Where spinal rod 40 is receivedwithin a rod channel 28, a fastener 42 can be loosely attached to thecorresponding collar 22 for capturing spinal rod 40 within the rodchannel 28.

A reduction jack 10 is next secured to each bone fixation screw 14.Where spinal rod 40 is already received within a rod channel 28, it isnot always necessary to secure a reduction jack 10 to that bone fixationscrew 14. However, because reduction jacks 10 also assist in derotationof vertebrae 15, a reduction jack 10 is typically secured to all bonefixation screws 14. During the attachment of a reduction jack 10,reduction sleeve 52 is initially positioned proximally on mounting stem50 so that reduction sleeve 52 is off of legs 90. Leg 90B thusresiliently pivots away from leg 90A. In this expanded configuration,legs 90 are advanced over collar 22 of bone fixation screw 14.Simultaneously, where spinal rod 40 is not already received within rodchannel 28 of bone fixation screw 14, spinal rod 40 is also capturedwithin rod channel 108 (FIG. 5) between legs 90.

Lever 210 of reduction sleeve 52 is then depressed releasing pawls 180from teeth 80. Reduction sleeve 52 is then manually slide distally downmounting stem 50 so as to collapse legs 90 onto the opposing sides ofcollar 22. Legs 90 are positioned so that as they collapse into theclosed position, catches 104A and B (FIG. 7) are received withinretention notches 30A and B (FIG. 2) on collar 22 so that the reductionjack 10 is secured to the corresponding bone fixation screw 14.Reduction sleeve 52 is slid distally until spinal rod 40 captured withinrod channel 108 is received within engagement grooves 134 (FIG. 9)located at the distal end of reduction sleeve 52.

Next, with legs 90 attached to collar 22 of bone fixation screw 14 andreduction sleeve 52 pushed against spinal rod 40, a driver is receivedwithin drive socket 160 (FIG. 12) of gear assembly 154 and rotated. Asgear assembly 154 rotates, reduction sleeve incrementally moves distallyalong mounting stem 40, as discussed above, so as to reduce or movespinal rod 40 distally along rod channel 108 of mounting stem 50 andinto rod channel 28 of the corresponding bone fixation screw 14. Themechanical advantage produced by gear assembly 154 assists in thereduction of spinal rod 40. When spinal rod 40 is sufficiently reducedinto rod channel 28, a fastener 42 can be mounted onto collar 22 so asto capture spinal rod 40 within rod channel 28. Fastener 42 can beattached by placing fastener 42 on the end of a driver and then usingthe driver to pass fastener 42 down through passageway 102 of mountingstem 50 to collar 22. The driver can then be used to thread fastener 42onto collar 22.

Once spinal rod 40 is captured within rod channel 28 of all bonefixations screws 14 and vertebrae 15 are all in the proper orientation,a driver can be used fully tighten fasteners 42 onto collars 22 sospinal rod 40 is securely fixed each bone fixation screw 14. In thisconfiguration, the vertebrae 15 to which spinal rod 40 is attached aresubstantially precluded from moving relative to each other. Reductionjacks 10 can then be removed. The removal is accomplished by depressinglever 210 so as to release pawls 180 and then manually sliding reductionsleeve 52 proximately along mounting stem 50 until leg 90B resilientlyoutwardly pivots so as to release collar 22.

Reduction jacks 10 have a variety of unique benefits. For example, as aresult of the ability to quickly release pawls 180, reduction sleeve 52can be quickly advanced along mounting stem 50 and positioned againstspinal rod 40 for subsequent reduction into rod channel 28 of bonefixation screw 14. One embodiment of the present invention thus enablesrapid attachment of reduction jacks 10 to bone fixation screws 14, rapidreduction of spinal rod 40 and rapid removal of reduction jacks 10 frombone fixation screws 14. Furthermore, because gear assembly 154 remainsengaged with teeth 80 when pawls 180 are released, there is less chanceof misalignment of gear assembly 154 with teeth 80 throughout use. Theuse of two offset pawls 180A and B also permits greater precision in thepositioning of reduction sleeve 52 and the reduction of spinal rod 40.Another benefit of one embodiment of the present invention is that gearassembly 154 and the driver socket thereon is openly exposed for easyattachment of a driver and thus easy movement of reduction sleeve 52.Other benefits also exist.

With reference to FIG. 4, each reduction jack 10 can also includeextension 54 that can removably couple to proximal end 66 of mountingstem 50. Extension 54 lengthens the reduction jack to permit greaterleverage for manipulating vertebrae 15. The inventive reduction jackscan thus have different lengths depending on their needed use. Asdepicted in FIG. 14, extension 54 comprises an outer sleeve 230 having aproximal end 232 and an opposing distal end 234 and an interior surface236 that bounds a passageway 238 extending therebetween. Interiorsurface 236 has a radially inwardly stepped shoulder 240. Outer sleeve230 includes an outwardly projecting brace 299 having an opening 300formed thereon.

A plunger 242 is configured to be received within passageway 238 ofouter sleeve 230. Plunger 242 comprises a tubular body 244 having aproximal end 246 and an opposing distal end 248. Mounted on proximal end246 is a cap 250 having an opening 252 that extends therethrough andcommunicates with passage 251. An annular gap recess 254 is formedbetween the bottom of cap 250 and body 244. A spring 256 is receivedwithin gap recess 254 and encircles body 244. A pair of mounting legs258A and B project from a distal end 248 of tubular body 244. Radiallyinwardly projecting from distal end of each mounting leg 258A and B is acatch 260A and B, respectively. Likewise radially outwardly projectingfrom the distal end of each leg 258A and B is a retainer 262A and B,respectively. Also radially outwardly projecting from each leg 258A andB adjacent to retainers 262A and B is a tapered ramp 264A and B,respectively. Ramps 264 are disposed proximal to retainers 262 and sloperadially outward as they extend toward retainers 262.

During assembly, the distal end of plunger 242 is advanced down throughpassageway 238 of outer sleeve 230 until spring 56 rests on innershoulder 240. Distal end 234 of outer sleeve is configured to radiallyinwardly compress mounting legs 258 such that when retainers 262A and Bpass beyond distal end 234 of outer sleeve 230, mounting legs 258resiliently outwardly expand so that retainers 262 project over thedistal end face of outer sleeve 230 and tapered ramps 264 rest againstthe interior surface of outer sleeve 230. In this configuration,retainers 262 prevent mounting legs 258 from unintentionally passingback up through passageway 238.

During attachment, as shown in FIG. 4, proximal end of plunger 242,i.e., cap 250, is manually depressed into distal end 232 of outer sleeve230 by compressing spring 256 therein. As a result, mounting legs 258distally project further beyond distal end 234 of outer sleeve 230. Asmounting legs 258 move further distally, ramps 264 are moved outside ofouter sleeve 230 which enables mounting legs 258 to further separate.The exposed separated legs 258 are then slidably received withincorresponding alignment channels 82 on proximal end 66 of mounting stem50 so that catches 260A and B are received within corresponding pockets84A and B. Plunger 242 is then released forcing distal end 234 of outersleeve 230 to encircle proximal end 66 of mounting stem 50 and to passover ramps 264. As outer sleeve 230 passes over ramps 264, legs 258 areradially inwardly compressed so as to lock catches 260 into pockets 84and thereby lock extension 54 to mounting stem 50. To remove extension54, the process is reverse. The attachment of extension 54 to mountingstem 50 gives greater length to reduction jacks 10 which allows greaterleverage for derotation or other manipulation of vertebrae 15 that maybe out of alignment. In alternative embodiments, it is appreciated thatextension 54 could be attached to mounting stem 50 using a variety ofother techniques.

In the assembled configuration, passage 251 extending through plunger242 aligns with passageway 102 extending through mounting stem 50 sothat a driver with fastener 42 thereon can be passed through the entirelength of extension 54 and mounting stem 50. Extension 54 typically hasa length in a range between 4 cm and 15 cm with between 5 cm and 12 cmbeing more common. Other lengths can also be used.

As depicted in FIG. 1, where desired, bridge 12 can extend betweenextensions 54 of adjacent reduction jacks 10 to help facilitatestabilization and desired orientation of the reduction jacks 10 and thecorresponding vertebrae 15. As depicted in FIG. 15, bridge 12 comprisesa first brace 266 and a second brace 268 that can be mounted tocorresponding extensions 54 and which can be adjustably telescopedrelative to one another to be fixed in a desired length. First brace 266comprises a tubular shaft 270 having a first end with a coupling pin 272hingedly mounted thereat and an opposing second end with a housing 274mounted thereat. Coupling pin 272 can be removably received withinopening 300 on extension 54 (FIG. 14) for securing first brace 266 toextension 54. A passageway 276 laterally extends through housing 274 andalong the length of shaft 270. Housing 274 has a top end 278 with anopening 280 formed thereat that communicates with passageway 276. Formedon the interior surface of housing 274 adjacent to passageway 276 is achannel 282.

Second brace 268 comprises a shaft 284 having a first end with acoupling pin 286 hingedly coupled thereto and an opposing second end287. Coupling pin 286 can be removably received within opening 300 on ofa corresponding extension 54 (FIG. 14) for securing second brace 268 toan extension 54. Formed along each opposing side of shaft 284 along thelength thereof are a plurality of locking slots 288. Shaft 284 isconfigured to telescope into and out of passageway 276 of shaft 270.

An engager 290 is configured to lock together shafts 270 and 284 atdesired telescoped positions. Engager 290 comprises a button 292 havinga U-shaped frame 294 projecting therefrom. Inwardly extending from thelower end of frame 294 are a pair of opposing flanges 296A and B. Frame294 is configured to be slidably received within channel 282 of housing274. A spring 298 is placed between a floor of housing 274 and thebottom of frame 294 to resiliently upwardly bias engager 290. Bydownwardly pressing on button 292 engager 290 is moved to a depressedposition wherein shaft 284 can freely telescope into and out ofpassageway 276 of shaft 270. When shafts 270 and 284 are in theirdesired position, button 292 can be released. Spring 296 then upwardlypushes engager 290 so that flanges 296A and B are received withincorresponding locking slots 288A and B on shaft 284, thereby lockingshaft 284 at a desired telescoped position within passageway 276.

It is appreciated that housing 274 and engager 290 can be replaced witha variety of different configurations so as clamps, fasteners, setscrews, and the like for securing braces 266 and 268 as relativepositions.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. A reduction jack for placing a spinal rod withina rod channel of a bone fixation screw, comprising: an elongated,tubular, mounting stem comprising: a tubular body; a plurality of teethdisposed on the body; a pair of legs attached to and projecting from thebody, at least a portion of the legs being separated by two spaced apartrod channels; and means disposed on the legs for engaging the bonefixation screw; a reduction sleeve at least partially encircling themounting stem, the reduction sleeve having a proximal end and anopposing distal end; a gear assembly mounted on the reduction sleeve,the gear assembly engaging the teeth on the body such that manipulationof the gear assembly facilitates movement of the reduction sleeve alongthe length of the mounting stem; and a first pawl pivotably mounted tothe reduction sleeve and resiliently biased against the teeth on thebody, the first pawl being pivotable between a first position where thefirst pawl engages the teeth on the body and a second position whereinthe first pawl does not engage the teeth on the body.
 2. The reductionjack as recited in claim 1, further comprising a lever mounted on thereduction sleeve, the lever being movable between a first position wherethe first pawl engages the teeth on the body and a second positionwherein the first pawl does not engage the teeth on the body.
 3. Thereduction jack as recited in claim 2, wherein the reduction sleeve canfreely slide in either direction along the length of the mounting stemwhen the lever is in the second position.
 4. The reduction jack asrecited in claim 3, wherein the gear assembly remains engaged with theteeth on body when the lever is in the second position.
 5. The reductionjack as recited in claim 1, further comprising a second pawl pivotablymounted to the reduction sleeve and resiliently biased against the teethon the body, the second pawl being offset from the first pawl so thatthe first and second pawl either simultaneously engage different teethor simultaneously engage different sides of the same tooth.
 6. Thereduction jack as recited in claim 5, further comprising a lever mountedon the reduction sleeve, the lever being movable between a firstposition where the first pawl and second pawl engage the teeth on thebody and a second position wherein the first pawl and second pawl do notengage the teeth on the body.
 7. The reduction jack as recited in claim1, wherein at least one of the legs of the mounting stem is hingedlycoupled to the body.
 8. The reduction jack as recited in claim 7,wherein the reduction sleeve can be moved between a first position whichpermits the at least one of the legs to outwardly pivot and a secondposition which prevents the at least one of the legs from outwardlypivoting.
 9. The reduction jack as recited in claim 1, wherein the meansfor engaging the bone fixation screw comprises a catch inwardlyprojecting from an interior surface of each leg.
 10. The reduction jackas recited in claim 1, wherein the gear assembly comprises: a first gearengaging the teeth on the body; a second gear connected to the firstgear; and a driver socket formed on the second gear such that rotationof the drive socket facilitates rotation of the second gear which inturn rotates the first gear, the gears being configured to produce amechanical advantage.
 11. The reduction jack as recited in claim 1,further comprising an extension removably coupled to the mounting stem.12. A spine fixation system comprising: a bone fixation screw having arod channel formed thereon; an elongated spinal rod received within therod channel of the bone fixation screw; and reduction jack comprising:an elongated, tubular, mounting stem comprising: a tubular body; aplurality of teeth disposed on the body; and a pair of legs attached toand projecting from the body and being removably coupled to the bonefixation screw; a reduction sleeve at least partially encircling thetubular stem, the reduction sleeve having a proximal end and an opposingdistal end, the distal end being biased against the spinal rod; a gearassembly mounted on the reduction sleeve, the gear assembly engaging theteeth on the body such that manipulation of the gear assemblyfacilitates movement of the reduction sleeve along the length of thestem; and a first pawl pivotably mounted to the reduction sleeve andresiliently biased against the teeth on the body, the first pawl beingpivotable between a first position where the first pawl engages theteeth on the body and a second position wherein the first pawl does notengage the teeth on the body.
 13. The spine fixation system as recitedin claim 12, further comprising a lever mounted on the reduction sleeve,the lever being movable between a first position where the first pawlengages the teeth on the body and a second position wherein the firstpawl does not engage the teeth on the body, wherein the reduction sleevecan freely slide in either direction along the length of the mountingstem when the lever is in the second position.
 14. A method foroperating a spinal reduction jack, the method comprising: coupling adistal end of a tubular mounting stem to a bone fixation screw having arod channel formed thereon, the distal end of a tubular mounting stemhaving a pair of rod channels formed thereon in which a spinal rod isreceived; moving a lever on a reduction sleeve that at least partiallyencircles the mounting stem to a second position so that a first pawldisengages from teeth on the mounting stem; with the lever in the secondposition, freely sliding the reduction sleeve along a length of themounting stem so that a distal end of the reduction sleeve is disposedagainst or adjacent to the spinal rod; moving the lever to a firstposition so that the first pawl engages the teeth; and manipulating agear assembly coupled to the reduction sleeve and engaging the teeth onthe mounting stem so that the distal end of the reduction sleeve reducesthe spinal rod into the rod channel of the bone fixation screw.
 15. Themethod as recited in claim 14, further comprising passing the shaft of adriver down through the mounting stem and coupling a fastener on theshaft to the bone fixation screw so as to secure the spinal rod withinthe rod channel of the bone fixation screw.
 16. The method as recited inclaim 14, wherein moving the lever to the second position causes thefirst pawl and a second pawl to disengage from the teeth on the mountingstem.
 17. The method as recited in claim 14, wherein the gear assemblyis engaged with the teeth on the mounting stem when the lever is in thesecond position.
 18. The method as recited in claim 14, furthercomprising: moving the lever back to the second position after thespinal rod has been reduced into the rod channel; and freely sliding thereduction sleeve on the mounting stem away from the spinal rod.